This invention relates to devices for use in the correction, arresting or slowing of abnormal curvature of the spine, including scoliosis, hyperlordosis and hypokyphosis.
Juvenile and adolescent scoliosis is a disorder of the growing spine in which a predominantly lateral curvature develops. Curves over 40° can require surgical correction due to the high risk of future progression during adulthood. One typical procedure, often called “posterior approach scoliosis surgery,” is one of the most invasive human surgeries in orthopedics. During a typical three to eight hour procedure, a surgeon strips the strong posterior muscles off of the spine for bone exposure, then attaches two metal rods to the spine with hooks, wires, or screws. An alternative scoliosis approach is through the anterior chest via thoracotomy or thoracoscopy. After multi-level discectomy and fusion, large screws are placed across the vertebral bodies, and then the screws and vertebrae are compressed together by means of a vertical rod.
Staples are often used in orthopaedics to fix two bones or pieces of bone together, such as would be required for osteotomy (bone cutting), or fracture stabilization. Staples typically used for these purposes are disclosed in U.S. Pat. Nos. 4,434,796 by Karapetian; 3,862,621 to Austin; 4,841,960 to Garner; 4,848,328 to Laboureau et al.; 5,449,359 to Groiso; 5,053,038 to Sheehan; and 4,913,144 to Del Medico.
Orthopaedic staples are also used in the fixation of soft tissue to bone, such as tendon or shoulder tissue. Staples typically used for these purposes are described in U.S. Pat. Nos. 5,352,229 to Goble et al.; 4,462,395 to Johnson; 4,570,623 to Ellison et al.; 4,454,875 to Pratt et al.; D320,081 to Johnson; and D340,284 to Johnson.
In addition, several screws with a linkage plate or rod have been developed for anterior spine fixation and are described in U.S. Pat. Nos. 5,324,290 to Zdeblick et al.; and 4,041,939 to Hall.
Additional U.S. Patents disclose spine staples, for example U.S. Pat. Nos. 4,047,523 to Hall; 4,047,524 to Hall; 5,395,372 to Holt et al.; D378,409 to Michelson; and D364,462 to Michelson.
The inventors have developed a novel procedure and spinal correction system for correcting scoliosis in children that takes advantage of future spine growth to correct the scoliosis. This procedure relies upon slowing spine epiphyseal growth on the convex side of the scoliosis curve with a novel hemiepiphyseal spinal correction system.
The novel procedure using the novel spinal correction system requires only about one-fourth of the time necessary for conventional implantation techniques and may be performed using minimally invasive endoscopic procedures. In addition, the novel spinal correction system has an extremely low profile which reduces the risk of neurological complications.
This new procedure illustratively uses a novel system of staples and screws to provide anterior non-fusion (no bone graft) correction of scoliosis in children with significant growth remaining. The procedure can be performed entirely endoscopically in as little as one hour of surgical time. This procedure using the novel spinal staple avoids the complex rod-screw linkage of current anterior scoliosis corrective systems. It also holds the potential for making correction an outpatient procedure and minimizes blood loss during surgery.
Existing spinal implants do not effectively take advantage of the hemiepiphysiodesis principle of altering spine growth and allowing for gradual correction through asymmetric growth. Prior art bone staples used to fix two bones or pieces of bone together, for example, are not designed to perform hemiepiphysiodesis, and are not designed or able to resist the forces of spinal motion and growth without significant splay. Orthopaedic staples used to fix soft tissue to bone are not designed to span two bones or two pieces of bone. Thus, such staples are inapplicable to the novel procedure for the correction of scoliosis in children.
The other staples mentioned above were not designed for spine hemiepiphysiodesis and are instead intended for other purposes. For example, U.S. Pat. No. 4,041,939 to Hall discloses small staples to stabilize a screw-bone interface and to prevent migration or plowing of a screw through a bone. Likewise, U.S. Pat. No. 4,047,524 to Hall discloses a spinal staple meant to stabilize the screw-bone interface of a screw and rod system. U.S. Pat. No. 4,047,523 to Hall discloses a surgical sacral anchor implant that is half of a staple blade affixed to a cable for the fixation of the lower end of the spine. U.S. Pat. No. 5,395,372 to Holt et al., is a spinal staple that holds a strut bone graft in place and is designed for use after vertebrectomy.
Thus, there exists a need for an effective spinal correction system that is small and designed to span vertebral endplate growth centers on either side of a disk.
Devices such as screws or staples for the treatment of skeletal deformity have been know to disrupt, or cut through, bone during normal use. More particularly, epiphyseal devices for the arrest or correction of spinal deformity may disrupt the surrounding bone due to high loads carried by the fastening mechanism, such as a staple leg. This disruption, often called “bone plowing,” occurs under physiological loads due to growth and to joint motion. Bone plowing can reduce the force magnitudes applied to the bone's growth plates and may also be associated with device deformation or dislodgment.
As a staple plows through bone it may partially dislodge such that the staple crown moves away from the bone. As the staple crown moves away from the bone, a greater moment is placed about the staple leg, which can cause the staple to deflect or plastically bend and splay open the legs. In severe cases, the staple may dislodge, resulting in other potential complications.
As such, there exists a need for an effective spinal correction system that reduces the likelihood of bone plowing by spreading the load over a large area of vertebral bone.